Rugged miniature electron tube



' Nov. 2-3, 1965 Q MARSDEN, JR 3,219,871

RUGGED MINIATURE ELECTRON TUBE Filed Sept. 5. 1952 INVENTOR. Churlea E Murlsd eIuIr.

ATTORN E Y5 United States Patent M 3,219,871 RUGGED MINIATURE ELECTRON TUBE Charles P. Marsden, Jr., Washington, D.C., assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 5, 1952, Ser. No. 308,175 9 Claims. (Cl. 313-243) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to subminiature electron tubes and more particularly to subminiature electron tubes for use in electric or electronic fuses and control devices employed in explosive projectiles, guided missiles and the like.

The requirements for military fuse operation include an oscillator tube which can withstand high shock from initial propulsion as well as low tube-noise output regardless of the vibrations of the missile in flight. The designs of currently available tubes incorporate an assembly wherein several members such as taut spring-tensioned filament and swaged grid lateral wires can vibrate excessively. These members are spaced by insulating members which support the assembly in the envelope of the tube. In this structure spot welds are used and are potential causes of mechanical weakness and vibration. The insulating members are subject to electron bombardment giving rise to secondary emission and/ or gas which are causes of noise, an effect similar to microphonics.

It is an object of the invention to provide an electron tube that is free from microphonics which cause undesired surges of current, leading to spurious indication and unreliable operation.

Another object of the invention is an electron tube so constructed as to withstand the forces of setback experienced in proximity fuses for artillery projectiles and rockets.

Another object of the invention is an electron tube designed to be negligibly affected by mechanical vibrations.

Another object of the invention is a new and novel cathode for subminiature electron tubes.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from the following description and accompanying drawings in which:

FIGURE 1 is an enlarged elevational view of the electron tube of the invention.

FIGURE 2 is a greatly enlarged perspective in cross section of the electron tube of FIGURE 1.

FIGURE 3 is an enlarged view taken along line 33 of FIGURE 2.

Referring now to the drawings wherein 1 is a truncated metal cone anode which also serves as the envelope of the tube. The base of cone 1 is terminated in a cup-shaped member 2 provided with a flange 3. A tubular member 4 terminates the opposite end of cone 1 and is provided with a lead or other appropriate seal 5. A vacuum-tight ceramic ring 6 is positioned in the cup-shaped member 2 and hermetically sealed thereto by means of lead seal 7. The lower surface 6a of ring 6 spaces the grid-cathode assembly 8 from the anode 1. A groove 9 of surface 6a has positioned therein a seal ring 10a for the purpose of holding the grid-cathode assembly and the anode together in hermetically sealed relationship. The grid-cathode assembly 8 comprises a truncated cone grid support element 10, having mounted on the top thereof a grid element 11 comprising an electrolytic nickel mesh. The truncated cone 10 of the grid-cathode assembly is provided with, a cup-shaped member 12 and a flange 13 similar to the cup-shaped member and flange of the anode 3,219,871 Patented Nov. 23, 1965 1. A vacuum-tight ceramic disk 14 is hermetically sealed in the cup-shaped member 12 by means of lead seal 15. Reference numerals 16 and 17 indicate cathode pins which are hermetically sealed as indicated by 20 and 21 in perforations 18 and 19 formed in disk 14. The insulating members 6 and 14 are shielded from electron bombard ment by the anode 1 and grid support element 10.

The hairpin cathode 22 has its legs spaced so that they are parallel to the truncated cone grid support element 10 and grid element 11 with the ends thereof welded to pins 16 and 17 as at 23. In order to obtain greater rigidity, the cathode is substantially semicircular in cross section which also permits a greater emitting surface facing the truncated cone grid support element 10 and grid element 11, and also overcomes the expansion and contraction problem existing in hot cathode emitters of the straight cylindrical construction or string type which vibrate and generate excessive noise voltage. Thus it can be seen that in addition to the novel cathode, the new and novel features of my subminiature tube are the improved properties as obtained by the construction involving metal and ceramic rather than metal and glass. By this means the various parts are supported directly by the ceramic and not by small support wires anchored in glass which lend themselves to mechanical vibration and create microphonics. Among the major objectionable characteristics of prior art subminiature tubes is the excessive amplitude of vibration of the grid and cathode elements which results in undesired surges of currents producing spurious indication and unreliable operation. In view of the fact that the amplitude of vibration of said elements is proportional to the mass, the grid mesh 11 and cathode 22 are fabricated from a metal of low density having a cross sectional thickness of less than one mil. The base metal from which cathode 22, described above, may be fabricated can be either zirconium or titanium. These base metals not only possess the advantage of low density, but a further advantage in that during the breakdown of the oxide-coating on the cathode 22, due to the evacuation and activation processes, some of the gas evolved from the coating is absorbed in the base metal. The solution of the gas into the base metal forms an alloy which results in a cathode of increased rigidity and resistance. Thus while the cathode was a metal of high ductility during fabrication, it is now an alloy of that metal with the properties of considerably increased strength.

Another advantage of the tube of invention is the construction and materials are such that the center of gravity is closer to the base of the tube a distance much less than than that of prior art subminiature tubes and, therefore, permits use of a heavy metal for the anode construction so that it can also serve as the envelope. This type of construction also prevents deformation of the elements and eliminate microphonics.

It will be apparent that the embodiment shown is only exemplary and that various modification can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

What I claim is:

1. A subminiature electron discharge device of the class described comprising a metallic comically-shaped anode serving as the envelope of said device, a comically-shaped grid element in spaced relationship to the anode, an insulating spacer maintaining said anode and grid element in spaced and hermetically sealed relationship, a second insulating member hermetically sealed to the base of said grid element and supporting an inverted V-shaped cathode of irregular cross section.

2. An electrode assembly for an electrical space discharge tube comprising a frusto-conical grid element support, a conical grid mesh aflixed to the top of the support, a metallic conical envelope comprising the anode, a vacuum-tight insulating means spacing the anode and support in hermetically sealed relationship, a hairpin cathode supported by a disk hermetically sealed to the base of said support, the legs of said cathode in parallel to said support and grid mesh.

3. A subminiature electron discharge device comprising a conically shaped metallic anode serving as the envelope of the device, a flange cup-shaped metallic member integral with the base of the conical anode, a conically shaped grid mesh supported by a frusto-conical member having a flanged base, a vacuum-tight ceramic ring positioned in said cup-shaped member and in contact with one surface of said flanged base in hermetically sealed relationship, a ceramic disk hermetically sealed to the opposite side of the flanged base, said disk supporting a hairpin cathode having a channeled surface facing said grid and parallel thereto.

4. A subminiature electron discharge tube of the class described comprising a conically shaped metallic anode forming the envelope thereof and provided with a flanged base, a conically shaped metallic grid element provided with a flanged base, a ceramic ring surrounding said conically shaped metallic grid element at its flanged based and spacing said flanged bases, the transverse surface of said ring adjacent the base of said grid element hermetically sealed thereto, the peripheral surface of said ring hermetically sealed to the base of said anode, a hairpin cathode supported by a ceramic disk, said disk hermetical- 1y sealed to the base of the grid-anode assembly.

5. The invention in accordance with claim 4 wherein said conically-shaped grid comprises a frusto-conically sheet metal element extending from said base into the conically shaped electro mesh grid supported thereon,

said conically-shaped sheet metal element shielding the ceramic ring from electron bombardment.

6. The invention in accordance with claim 5 wherein said hairpin cathode is a substantially V-shaped ribbon of ductile metal having a semicircular cross section.

7. The invention in accordance with claim 6 wherein the cathode comprises a channelized oxide coated Zirconium ribbon,

8. The invention in accordance with claim 6 wherein the cathode comprises a channelized oxide coated titanium ribbon.

9. A subminiature electron discharge device comprising an assembly of a fragile conically-shaped metallic anode serving asan envelope of the device, a flanged cup-shaped metallic member integral with the base of the conical anode, a conically-shaped grid mesh supported by a frustoconical member having a flanged base, a vacuum-tight ceramic ring positioned in said cup-shaped member and in contact with one surface of said flanged base in hermetically sealed relationship, a ceramic disk hermetically sealed to the opposite side of the flanged base, said disk supporting a hairpin cathode having a channeled surface facing said grid mesh, said ring and disk positioned in said assembly whereby the center of gravity is adjacent the base of said assembly to prevent deformation of the anode and grid mesh.

References Cited by the Examiner UNITED STATES PATENTS 2,115,934 5/1938 Smith 313-341 2,121,600 6/1938 Knowles 313-265 2,634,384 4/1953 Ford "a 3l3-318 JOHN W. HUCKERT, Primary Examiner.

ROGER L. CAMPBELL, Examiner. 

1. A SUBMINIATURE ELECTRON DISCHARGE DEVICE OF THE CLASS DESCRIBED COMPRISING A METALLIC CONICALLY-SHAPED ANODE SERVING AS THE ENVELOPE OF SAID DEVICE, A CONICALLY-SHAPED GRID ELEMENT IN SPACED RELATIONSHIP TO THE ANODE, AN INSULATING SPACER MAINTAINING SAID ANODE AND GRID ELEMENT IN SPACED AND HERMETICALLY SEALED RELATIONSHIP, A SECOND INSULATING MEMBER HERMETICALLY SEALED TO THE BASE OF SAID GRID ELEMENT AND SUPPORTING AN INVERTED V-SHAPED CATHODE OF IRREGULAR CROSS SECTION. 